Shadow mask mounting structure



g- 1, 1967 T. M. SHRADER 3,334,259

SHADOW MASK MOUNTING STRUCTURE Filed June 12, 1964 2 SheetsSheet 1 1, 1957 T. M. SHRADER SHADOW MASK MOUNTING STRUCTURE 2 Sheets-Sheet 2 Filed June 12, 1964 INVENTOR. 756?) M 3%405? far/2:0

United States Patent 3,334,259 SHADOW MASK MOUNTING STRUCTURE Terry M. Shrader, Leacock, Pa., assignor to Radio Corpo ration of America, a corporation of Delaware Filed June 12, 1964, Ser. No. 374,587 3 Claims. (Cl. 31385) This invention relates to cathode ray tubes and particularly to the structure and fabrication of an electrode therefor wherein apertured spring support straps are attached to the electrode and disposed over a plurality of support studs for removably mounting the electrode.

In some types of cathode ray tubes, an electrode of substantially the same size as the phosphor screen of the tube is mounted closely adjacent to the screen. For example, the shadow mask cathode ray tube for producing images in color includes a multiapertured masking electrode which may be spaced about /2-inch from a mosaic phosphor screen. The commercially available RCA 2lFBP22 is such a tube.

The envelopes of tubes which have an electrode mounted adjacent to the screen usually include a shallow bowl-like glass faceplate panel sealed to a glass funnel member. The faceplate panel comprises a curved faceplate portion on which the phosphor screen is disposed and a peripheral sidewall portion. A plurality of studs are sealed into or onto the internal surface of the sidewall of the panel. The mask electrode is removeably mounted on the studs by a plurality of strap-1ike springs which are attached to the mask and which have apertures therein into which the studs fit.

It is an object of this invention to provide an improved method for attaching the support springs to the shadow mask electrode of a cathode ray tube.

It is also an object of this invention to provide an improved assembly of faceplate panel and shadow mask electrode for a cathode ray tube.

Another object of this invention is the provision of an improved mounting spring for a shadow mask'electrode.

In accordance with the invention, a shadow mask electrode such as described above is positioned within a faceplate panel and spaced from the faceplate thereof preferably by a spacer device interposed therebetween. The panel includes a plurality of suitable electrode support studs extending inwardly thereof. One or more apertured spring elements are then placed over their associated studs and then fixed to the electrode such as by welding.

Preferably, the apertured spring element constitutes a part only of the complete spring and comprises a washer whose aperture is adapted to snugly receive a stud therein.

In this case a separate spring strap with an aperture at one end larger than the stud is provided which is welded at the other end to the frame. The washer is welded to the apertured end of the spring strap to complete the spring.

Alternatively, the apertured spring element may comprise the complete spring, which is welded near one of its ends to the electrode assembly and isapertured near its free other end to receive the stud. By either alternative, at least one, and preferably all, of the apertured spring elements are secured to the electrode assembly in precise .alignment with their associated panel studs.

According to the prior art, often thestuds are attached to a faceplate panel by the use of one jig and the support springs are attached to the mask electrode by the use of a different but related jig. The resulting tolerance of fit of the mask on the studs and the tolerance of the mask-to-' screen spacing is accordingly determined by the additive tolerances of the two jigs. The present method avoids the inaccuracies of such additive tolerances. The studs themselves are used as the locating jigs for securing the aperaccurate spacing of the mask electrode from the faceplate.

In a tube wherein the mask electrode is supported on three studs (3-stud system), the inaccuracies of the prior art method of using two separate jigs may not be detrimental to the fit of the mask on the studs. However, it will be detrimental to an accurate establishing of maskto-screen spacing. In a tube wherein the mask electrode is supported on four studs (4-stud system) the inaccuracies of the 2-jig prior art method will be detrimental to both the fit of the mask on the studs and to the mask-toscreen spacing. The improved accuracy of fit between the mask electrode and the studs obtained by my'rnethod is therefore especially advantageous in a 4-stud system such as has been proposed for a shadow mask cathode ray tube having a rectangularly shaped faceplate and mask electrode.

With the general type of spring-stud arrangement described herein, a 3-spring mask can always be fitted onto its 3-stud panel even though, due to manufacturing tolerances, the spring aperture array and the stud array are not identically disposed. This is because the mask can be shifted and rotated slightly until each of the three spring apertures is in alignment with its associated stud. Furthermore, the three springs Will be received on the three studs with the mask in only one position. That is, a 3-point support arrangement of three springs on three studs determines a unique position of the mask relative to the panel. Thisis true not only for a 3-stud support system, but also for three of the four supports of a 4-stud support system. Thus, in a 4-stud system, the fourth spring and the fourth stud must be positioned so that they mate precisely with each other when the mask is in the unique position determined by the other three supports. Manufacturing tolerances of the prior art methods described above do not permit such precise positioning to be readily obtained.

In the drawing:

FIG. l'is a plan view of a cathode ray tube faceplate panel and apertured mask electrode together with a spacing fixture utilized in securing the apertured spring elements to the mask electrode assembly;

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is an enlarged sectional view of a portion of the device of FIGS. 1 and 2 taken along line 33 of FIG. 2;

FIG. 4 is an exploded perspective view of the stud and a portion of the spring support of FIG. 3; and

FIGS. 5 and '6 are perspective and exploded perspective views of respectively alternative embodiments of spring supports.

With reference to the drawing, a cathode ray tube glass faceplate panel 10 comprises a generally rectangular faceplate 12 and a sidewall 14 extending from the periphery of the faceplate. The faceplate 12 is preferably curved, e.g., with an approximately spherical contour, as is known in the art. A plurality of electrode mounting studs 16 extend from the interior surface of the panel sidewall 14. The studs 16 may be bonded to the surface of the sidewall with, e.g., a glass frit, or they may be embedded in 'the sidewall by a conventional glass-tometal seal. In a preferred arrangement, four studs are provided, one near'each of the mid-points of each of the two long sides 18 of the sidewall 14 and the two short sides 20 of the sidewall 14. Each stud 16 (FIGS. 3 and 4) comprises a cylindrical base 21 and a frusto-conical tip 22.

A shadow mask electrode 24, mounted within the faceplate panel 10, includes a frame member 26 and a masking member 28. The frame 26 comprises a generally rectangular loop-shaped rim having an L-shaped cross section. The masking member 28 comprises a shallow bowl-like multiapertured sheet of metal mounted across the frame 26. The masking member 28 has a surface contour which approximately matches the surface contour of the faceplate 12, for example, as described in US. Patent 3,109,116 issued to D. W. Epstein et al., on Oct. 29, 1963.

A plurality of support springs 29 are attached to the electrode 24 and support it on the studs 16. As best shown in FIGS. 3 and 4, each of the support springs 29 has one of its ends attached to the side of the frame 26 such as by spot welds at points 30. The other end of each spring 29 is off-set outwardly from the side of the frame and provided with a stud-receiving aperture 31. The offset may be provided by suitably bending the springs 29 along a line 32 thereacross. The springs are located so that their apertures 31 receive the frusto-conical tips 22 of the studs 16 to removably mount the mask electrode 24 within the panel 10. The mask electrode 24 may be removed and/or re-mounted by depressing the support springs 29 toward the frame 26 and free of the studs 16.

Each spring 29 preferably comprises a leaf spring strap element 33 and a Washer or apertured element 34. The strap 33 is provided near its free end with an opening 35 which is considerably larger than the stud tip 22 on which the spring 29 is seated. The washer 34 is provided with the stud-receiving aperture 31 in which the stud tip 22 is snugly seated. The aperture 31 is preferably shaped to contact the stud tip 22 in three triangularly spaced locations. For example, the aperture 31 may include three inwardly projecting fingers 36 which are suitably shaped to mate with the stud tip 22. The diameter of the washer opening 31 is intermediate the maximum and minimum diameters of the frusto-conical stud tip 22, as shown in the drawing, in order to snugly fit the stud tip. The washer 34 is disposed flush against the strap 33 on the stud side thereof, i.e. between the strap 33 and the sidewall 14 of the panel 10, with the stud-receiving aperture 31 in the washer overlying the large opening 35 in the strap. The large size of the strap opening 35 permits the strap 33 to loosely receive the stud tip 22 and the washer 34 to be adjustably positioned on the strap 33 to obtain a desired alignment with the associated stud 16. The strap 33 includes a tab 37 to facilitate depression of the strap during attachment of the washer 34 thereto.

The opening in the strap 33 over which the stud-receiving aperture lies need not be completely surrounded by portions of the strap 33 as is the opening 35. Instead the opening may be, e.g., a U-shaped cut-out extending inwardly from an edge of the strap 33.

Although a 2-piece support spring 29 as described above is preferred, a one-piece spring 38 as shown in FIG. may be used. In such case the separate washer 34 is omitted. Instead the spring 38 comprises the equivalent of a strap 33 with a stud-receiving aperture 31 instead of the opening 35. As hereinafter pointed out, the twopiece support spring 29 described above is preferred because it affords a more facile mask fabrication procedure than does the one-piece support spring.

In fabricating the assembly of panel and mask electrode 24, the multiapertured mask member 28 and the straps 33 are first mounted on the frame 26 according to known techniques. This mask-frame-strap assembly 28, 26, 33 (hereinafter referred to simply as the mask assembly) is then positioned on top of a spacer device 39 within the faceplate panel 10, to accurately establish a desired mask-to-screen spacing. The panel may be oriented open-end-up as shown in FIG. 2 so that gravity urges the mask assembly 28, 26, 33 against the spacer 39 and the spacer against the panel 10. The spacer device 39 includes a T-shaped member whose three arms 40, 40,

41 extend to adjacent to the panel sidewall 14. Spacer pads 42 are provided near the ends of the arms 40, 40, 41 and extend therefrom to contact the faceplate 12. Masksupport brackets 44 are attached to the ends of the spacer arms 40, 40, 41 for receiving the mask assembly 28, 26, 33 in desired relationship with the faceplate 12.

Other types or designs of spacer devices may be used in place of the spacer device 39.

If desired, the panel 10, spacer 39, and mask assembly 28, 26, 33 may be inverted, with the mask assembly 28, 26, 33 being supported and the panel 10 resting thereupon.

With the mask assembly 28, 26, 33 in position Within the faceplate panel 10, the straps 33 are depressed toward the frame 26 and the washers 34 are inserted over the studs 16 between the straps 33 and the studs, with the stud tips 22 snugly received within the apertures 31. In such an arrangement, the spring action of the straps 33 urges the washers 34 against the frusto-conical tips 22 of the studs 16 to keep the Washers in place. The tabs 37 on the straps are helpful in facilitating depression of the straps since a fabricators finger or spring depressor tool can conveniently be applied to the tabs.

At this point of the fabrication procedure, the washers 34 are still free to move relative to the straps 33; and the mask assembly 28, 26, 33 and spacer device 38 are still free to be urged together and against the faceplate 12. Thus, in this condition, the operator now establishes a precisely desired spacing between the mask member 28 and the faceplate 12 and a precise alignment of the stud-receiving apertures 31 of the washers with the studs 16.

The washers 34 are then secured to the straps 33 such as by a suitable welding thereof. It has been found preferable to provide only a temporary tack weld at this stage. Then, with the completely assembled mask electrode 24 removed from the panel 10 (by depressing the straps 33) a more secure weld using larger equipment is provided. The reason for making the initial tack weld is that the larger welding equipment cannot be easily fitted into the available space between the frame 26 and panel sidewall 14 when the mask assembly 28, 26, 33 is disposed in the panel 10.

As hereinbefore stated, a one-piece spring 38 may be used. Such a one-piece spring may be considered to integrally include the washer 34. In such case, a mask-frame assembly of the multiapertured mask member 28 and the frame 26 is disposed in the panel 10 on the spacer device. The one-piece springs 38 are then inserted over the studs 16 and welded to the mask frame 26 in a manner similar to the procedure described above. Means (not shown) is provided for holding the one-piece springs 38 against the frame 26 while they are being welded. As with the preferred procedure using the 2-piece springs 29, a fabrication procedure using one-piece springs provides the desired mask-to-faceplate spacing and the custom alignment of stud-receiving apertures 31 with their associated studs 16.

The above-described methods of attaching the spring apertured elements-either as an integral one-piece spring 38 or as a separate washer 34 of a 2-piece springrelative to the frame 26 may be used to secure either all of the support springs or any partial number of them, to the frame 26. For example, in a 4-stud panel, three support springs may be secured to the frame by prior art methods. Then the mask-frame assembly with the three springs may be supported within the panel using the three existing springs. The fourth spring apertured element is then secured to the frame 26 as hereinbefore described. In such a fabrication procedure, the spacing device 39 may be dispensed with since the mask can be supported in place within the panel by the three existing springs during the securing of the fourth apertured spring element. Attachment of only one apertured spring element by my method will provide the custom alignment highly desired in positioning the fourth spring of a 4-spring mask electrode 24.

FIG. 6 illustrates a support spring 50 which embodies the 2-piece spring feature of the invention and which can be substituted for the spring 29.

The spring 50 comprises a V-shaped spring strap 52 having a central portion 54 in which the large opening 35 is provided. The washer 34 is adjustably positioned flush against the strap portion 54 with the stud-receiving aperture 31 overlying the opening 35. The strap 52 is attached at points 56 by spot welds to the mask frame 26. The legs of the V-strap 52 are bent along the bend-lines 58 to space the aperture 31 away from the mask frame.

What is claimed is:

1. In a cathode ray tube of the type including a faceplate panel, four electrode support studs symmetrically distributed about and attached to said panel, and a multiapertured electrode mounted on said studs in a predetermined spatial relationship with said panel; the improvement which comprises:

a strap-like support spring having one end secured to said electrode and the other end spaced from said electrode, said other end having an aperture larger than said studs loosely receiving one of said studs,

a washer-like element located between said panel and said other end of said support spring and having an aperture therein snugly receiving said one of said studs,

said washer-like element being permanently secured to said support spring near its said other end with the portion of the surface of the spring adjacent to the surface of the washer-like element selected to effect said predetermined spatial relationship.

2. In a cathode ray tube of the type including a faceplate panel comprising a faceplate, a peripheral side wall, and a plurality of electrode support studs extending from the interior surface of said side wall, and a multiapertured shadow mask electrode mounted on said studs in a predetermined spaced relationship with said panel; the improvement which comprises:

a plurality of strap-like support springs each having one end secured to the periphery of said electrode and its other end spaced from said electrode, said "other end of each spring having an opening therein larger than said studs loosely receiving one of the studs,

a plurality of washers each located between said side wall and said other end of one of said support springs and having an aperture therein snugly receiving one of said studs,

each of said washers being permanently secured in flush face-to-face contact to the corresponding one of said support springs with the portion of the surface of the spring adjacent to the surface of the washer selected to effect said predetermined spaced relationship.

3. In a cathode ray tube, a faceplate panel, a plurality of frustoconical electrode support studs extending from said panel, a multiapertured shadow mask electrode, and a plurality of apertured means attached to said electrode and adapted to receive said studs in the apertures thereof for mounting said electrode in a predetermined spaced relationship with said panel, at least one of said means comprising a strap-like support spring having one end secured to the periphery of said electrode, said spring being bent to space the other end thereof from said electrode, said other end having an opening therein larger than said studs loosely receiving one of the studs, a washer located between said side wall and said other end of one of said support springs and having an aperture therein with a diameter intermediate the maximum and minimum diameters of said frustoconical studs snugly engaging one of said studs, said washer being located between said panel and said support spring, with said support spring resiliently urging said washer against the frustoconical surface of said stud, and permanently secured to said support spring with the portion of the surface of the spring adjacent to the surface of the washer selected to effect said predetermined spaced relationship.

References Cited UNITED STATES PATENTS 2,922,063 1/1960 Haas 313- JAMES W. LAWRENCE, Primary Examiner,

ROBERT Examiner, 

1. IN A CATHODE RAY TUBE OF THE TYPE INCLUDING A FACEPLATE PANEL, FOUR ELECTRODE SUPPORT STUDS SYMMETRICALLY DISTRIBUTED ABOUT AND ATTACHED TO SAID PANEL, AND A MULTIAPERTURED ELECTRODE MOUNTED ON SAID STUDS IN A PREDETERMINED SPATIAL RELATIONSHIP WITH SAID PANEL; THE IMPROVEMENT WHICH COMPRISES: A STRAP-LIKE SUPPORT SPRING HAVING ONE END SECURED TO SAID ELECTRODE AND THE OTHER END SPACED FROM SAID ELECTRODE, SAID OTHER END HAVING AN APERTURE LARGER THAN SAID STUDS LOOSELY RECEIVING ONE OF SAID STUDS, A WASHER-LIKE ELEMENT LOCATED BETWEEN SAID PANEL AND SAID OTHER END OF SAID SUPPORT SPRING AND HAVING AN APERTURE THEREIN SNGULY RECEIVING SAID ONE OF SAID STUDS, SAID WASHER-LIKE ELEMENT BEING PERMANENTLY SECURED TO SAID SUPPORT SPRING NEAR ITS SAID OTHER END WITH THE PORTION OF THE SURFACE OF THE SPRING ADJACENT TO THE SURFACE OF THE WASHER-LIKE ELEMENT SELECTED TO EFFECT SAID PREDETERMINED SPATIAL RELATIONSHIP. 